NATIONAL TRANSPORTATION SAFETY BOARD Office of Research and Engineering Washington, D.C. 20594 February 15, 2002 Recorded Radar Data Study American Airlines Flight 11 United Airlines Flight 175 American Airlines Flight 77 United Airlines Flight 93 by Daniel R. Bower, Ph.D. A. SUBJECT AIRCRAFT Location: New York City, NY Date: September 1 1 , 2001 Time: 08:47 AM Eastern Daylight Time Flight: American Airlines Flight 1 1 Aircraft: Boeing 767 NTSB#: DCA01 MA060 Location: New York City, NY Date: September 1 1 , 2001 Time: 09:03 AM Eastern Daylight Time Flight: United Airlines Flight 175 Aircraft: Boeing 767 NTSB#: DCA01 MA063 Location: Arlington, VA Date: September 1 1 , 2001 Time: 09:38 AM Eastern Daylight Time Flight: American Airlines Flight 77 Aircraft: Boeing 757-200, registration: N644AA NTSB#: DCA01 MA064 Location: Shanksville, PA Date: September 1 1 , 2001 Time: 1 0:03 AM Eastern Daylight Time Flight: United Airlines Flight 93 Aircraft: Boeing 757-200, registration: N591UA NTSB#: DCA01MA065 1 B. GROUP Daniel Bower, Ph.D. Senior Aerospace Engineer NTSB, RE-60 490 L’ Enfant Plaza E, SW Washington, DC 20594 C. SUMMARY This document describes information obtained from various sources of recorded radar of the subject aircraft both before and after the hijacking events, and a general overview of the time correlation of the data for all four aircraft with other data sources. Time synchronized ground tracks of the hijacked aircraft are presented. D. RADAR DATA Section I - Data Sources Air Route Surveillance Radar (ARSR) data was obtained from the FAA’s New York, Washington, Boston, and Cleveland Air Route Traffic Control Centers (ARTCC), output using the National Track Analysis Program (NTAP). ARSR radar data was also obtained from the United States Air Force 84 th Radar Evaluation Squadron (84 th RADES). Airport Surveillance Radar (ASR) data was acquired from several airport facilities’ Terminal Radar Control (TRACON) areas. ASR radar normally records data approximately every 414 seconds, but ARSR data is only recorded every 12 seconds. Both primary 1 radar data and secondary radar returns were recorded in the various radar data sets. The accuracy of the radar returns decreases with increasing distance from the radar sites. Since the relative distances of all the radar sites are different, there is a differing amount of error in the position of the aircraft determined from each radar source. An effort was made to account for the error in each radar data set, such that the best alignment of all radar data sets was achieved. The typical range for the ASR antennas is approximately 60 miles, so ASR information was obtained from those sites that captured the radar returns for the final portions of the flights in New York City. The USAF RADES data were obtained to capture the entire flights, from the initial radar contact with the 1 A “primary only target is received as a reflection of radar energy only. A “secondary” or “beacon” only target is recorded as a response of the aircraft’s transponder to interrogation by the radar system. A “reinforced” target is recorded by the radar system in lieu of a primary or secondary target when transponder information is coincident with and reinforces a reflection of radar energy. Generally, secondary and reinforced returns are referred to as “secondary targets. 2 RADES facilities to the final radar returns. Since the RADES data covers the entire east coast of the United States, the RADES data contained all of the data for all of the flights in a consistent time base. The FAA provided the ASR range/azimuth transponder secondary radar data and primary radar data for the hijacked flights. The data included radar clock time, range from the respective ASR radar antenna, magnetic azimuth angle, and flight level. The format supplied by the FAA for the ASR data contains time in hours, minutes, seconds, range from the radar site in nautical miles (NM), azimuth in ACP’s (4096 ACP’s = 360°), flight level in 100’s of feet-msl, and beacon codes. The range-azimuth-altitude format for each data set was converted to latitude-longitude-altitude format using site data for each ASR radar site 2 . NTAP data and USAF RADES data was obtained in latitude-longitude- altitude format. Occasionally, the clock time of day recorded at the individual radar sites may not be consistent. Since transponder altitude is recorded in every aircraft data set, the altitude data is a common piece of information for all the radar data. For example, if an aircraft is ascending after takeoff, it should pass through 10,000 feet altitude at the same time of day at every radar site. In cases of inconsistencies, the time of day of a radar data set must be adjusted to be consistent in altitude and time. The time of day at the airport ASR facilities is set at each facility, such that each ASR facility’s radar data could have a slightly different time of day. In this study the time of day used as the standard time is from the USAF 84 th RADES data, which covers all of the flights from takeoff to respective impacts. Initial comparisons of the radar data from the USAF and the FAA showed that an offset in time was present. The 84 th RADES found that the clock for the North East Air Defense Sector (NEADS) lagged the clocks for the other sectors by 25.3 seconds. The other sectors were all in agreement with the Global Positioning Satellite (GPS) time. Therefore, 25.3 seconds must be added to the radar data from the 84 th RADES. Comparison of the altitude data from the various NTAP centers and RADES showed no offset in time required for the FAA data from Washington, Cleveland, and Boston centers. An offset of 8 seconds was corrected in the NTAP radar data from New York center to align with the time of day from the RADES and other center NTAP radar data sets. The ARSR-4 long-range radar systems utilized by the FAA and the USAF have the capability to estimate the altitude of primary targets with a certain degree of accuracy. This capability is only available from the ARSR antennas 2 The range-azimuth-altitude format for each data set was converted to latitude-longitude-altitude format using the appropriate magnetic variation and antenna elevation for each radar site, with a WGS84 Earth surface model. 3 that have been specially modified for this purpose. The published 3 root-mean square accuracy of the height estimated by the radar system is +/- 3000 feet. After 08:21 EDT, American Airlines flight 1 1 no longer contained transponder altitude information. However, primary returns in the 84 th RADES data contained radar-derived heights for the remainder of the flight. Section II - Time Correlation A time correlation was made between the RADES radar data, NTAP radar data, ASR radar data sets, FDR data (when available), and Air Traffic Control (ATC) radio transmission transcript data. Times indicated with the USAF RADES radar data were used as the reference time, and the FDR and ATC clocks were adjusted accordingly. Times given in this report are in 24-hour format, in the form HH:MM:SS Eastern Standard Time (EST). The FDR records information relative to an elapsed time in seconds, and are assigned a time of day correlation using the technique outlined below. A comparison of the radar altitude versus local time for the several radar data sets with the FDR data (UAL83 and AA77) provided the basis for correlating the respective FDR data to the time of day. FDR altitude versus elapsed time was transposed to the radar data time of day using a single anchor point, i.e. a specified number of elapsed seconds on the FDR = 00:00:00 EDT. This anchor point is different for each FDR, and is further verified using radio callouts on the ATC transcript and microphone keying on the FDR. As discussed in a previous section, transponder altitude data was recorded from several radar facilities. All of the radar systems from the USAF RADES utilized the same time of day clock, and this time of day was also consistent with the adjusted NTAP and ASR radar time of day. After the correlation was applied to the FDR data, the ATC transcript provided an additional check of the correlation for the radio transmissions. All the FDR and radar data in this report are given in the correlated local time (EDT). Refer to the FDR Factual Report for FDR data extracted for UA flight 93 and AA Flight 77. Section 111 — Radar Data The recorded radar data from the various sources is contained on a CD- ROM. The data is organized with separate directories for the data for each flight. Within each flight’s directory are subdirectories that contain data either from a specific source as labeled, or combined from several sources to capture the flight. There are also directories for data that contains returns for all of the flights together in the same files. The directory structure is shown below, and this 3 Both the FAA and 84 th RADES have documented the capabilities of the radar sensing antennas in their respective technical manuals. 4 section provides a brief description of each file in the directories and sub directories. Radar Data CD-ROM Directory structure QHDK a Q AALll I j- ta AALll N90 i-Q AALll processed and misc I [ Q AALll ZBW ■ Cl AALll ZNY B-Q AAL77 I i-Q AAL77 LAD and DCA ■C) AAL77 misc and processed | I- Q AAL77 ZDC | 1-Q AAL77 ZID | Q Airforce i-Q Combined i-Q PACES $ Q UAL 175 i- Q UAL 175 misc and processed Q UAL 175 N90 | Q UAL 175 ZBW Q UAL 175 ZNY B Q UAL93 i- Q Processed UAL93 j I-Q ZDC UAL93 i-Q ZNY UAL93 j - Q job UAL93 1 Q Underlying ASRs List of Files: American Airlines Flight 1 1 Source \AAL1 1\AAL1 1 N90 AAL1 1 EWR TATU 1240 to 1248.txt p AA AAL1 1 SWF TATU 1 229 to 1 246.txt FAA EWR ASR UAL1 75 and AAL1 1 1 235 to 1 300.zip FAA EWR ASR UAL175 and prim 1300 to 1315.zip FAA EWR ASR UAL1 75 corrected beacons.txt F AA HPN ASR UAL175 and AALll 1230 to 1300.zip FAA ASR UAL175 beacons and primaries in WTC area.txt FAA JFK ASR UAL175 and AALll 1230to 1300.zip FAA JFKASRUAL175 and prim 1300to1315.zip FAA 5 JFK ASR UAL175 corrected beacons.txt N90 ERIT no coords 1200 to 1230.rs3 N90 ERIT no coords 1230 to 1300.rs3 N90 ERIT no coords 1300 to 1330.rs3 N90 TATUTG unk site 1 235 to 1 305.txt N90 TATUTG unk site 1 235 to 1 305a.txt FAA 84 th RADES 84 th RADES 84 th RADES FAA FAA Read Me.txt SWF ASR UAL1 75 and AAL1 1 1 230 to 1 300.zip FAA ...\AAL11\AAL11 Processed and misc 1 AAL1 1 ACARS messages.txt Aall 1 back converted from RVP - don't use targets with D.urf Aall 1 EWR RAPTOR procesed 1240 to 1247.txt AAL1 1 primaries including height.txt Aalll RAPTOR processed unknown site.txt Aall 1 trimmed from RS3.rad aall 1 trimmed from RS3.txt 84 th RADES FAA 84 th RADES FAA 84 th RADES 84 th RADES ...\AAL11\AAL11 ZBW aalll zbw prim 1219 to 1235.txt AAL11 ZBW prim 1233 to 1315.txt aalll zbw prim 1235 to 1248.txt ZBW AAL1 1 beacon only 1 155 to 1300.txt FAA FAA FAA FAA ...\AAL11\AAL11 ZNY aalll zny 1238 to 1240 prim.txt aalll zny 1240 to 1243.txt aalll zny 1242 to 1246.txt aall 1 zny 1245 to 1249.txt aall 1 zny 1245 to 1249a.txt FAA FAA FAA FAA FAA American Airlines Fliqht 77 ...\AAL77 crw91 1 01 .txt FAA 6 . . .\AAL77 IAD and DCA AAL77 DCA ASR 1300 to 1400.txt AAL77 IAD ASR 1210 to 1400.txt FAA FAA ...\AAL77\AAL77 misc and processed Aal77 back converted - don't use D targets.urf Aal77 export from RS3.rad aal77 export from RS3.txt 84 th RADES 84 th RADES 84 th RADES ...\AAL77\AAL77 ZDC Aal77 zdc 1320 to 1339.txt aal77a zdc 1 303 to 1 321 .txt Aal77a1 zdc 1258 to 1306.txt Aal77a2 zdc 1256 to 1302.txt Aal77a3 zdc also 1256 to 1302.txt aal77czdc 1220 to 1249.txt ZDC AAL77 NTAP 6553 code.txt FAA FAA FAA FAA FAA FAA FAA ...\AAL77\AAL77 ZID AAL77 zid 1234 to 1258 beacon only.txt ZID AAL77 beacon only.txt ZID AAL77 priml.txt ZID AAL77 prim2.txt ZID AAL77 prim4.txt ZID bad NTAP.txt FAA FAA FAA FAA FAA FAA Air Force Data (all fliqhts) ...\Airforce First.edt second, edt Septl 1_a.edt.xls 84 th RADES 84 th RADES 84 th RADES ...\Combined all four from RS3.rad 84 th RADES 7 filtered RS3 export showing all four airplanes.urf 84 th RADES filtered RS3 export showing all four airplanes.xls 84 th RADES N90 post impact TATU etc.txt FAA ..ARADES 12541 200. rs3 84 th RADES 12541230. rs3 84 th RADES 12541 300. rs3 84 th RADES 12541 330. rs3 84 th RADES 12541 400. rs3 84 th RADES 12541 430. rs3 84 th RADES RADES timeline.doc 84 th RADES United Airlines Flight 175 . . AUAL1 75\UAL1 75 misc and processed N90 RAPTOR processed 1 234 to 1 303.txt FAA UAL 175 ACARS messages.txt Ual175 export from RS3.rad 84 th RADES ual175 export from RS3.txt 84 th RADES .. AUAL175MJAL175 N90 EWR ASR UAL1 75 and AAL1 1 1 235 to 1 300.zip FAA EWR ASR UAL1 75 and prim 1 300 to 1 31 5.zip FAA EWR ASR UAL175 corrected beacons.txt FAA HPN ASR UAL175 and AAL11 1230 to 1300.zip FAA ASR UAL175 beacons and primaries in WTC area.txt FAA JFK ASR UAL1 75 and AAL1 1 1230to 1300.zip FAA JFK ASR UAL1 75 and prim 1 300 to 1 31 5.zip FAA JFK ASR UAL175 corrected beacons.txt FAA N90 ERIT no coords 1200 to 1230.rs3 84 th RADES N90 ERIT no coords 1230 to 1300.rs3 84 th RADES N90 ERIT no coords 1300 to 1330.rs3 84 th RADES N90 RT unk site 1 300 to 1 307.txt FAA N90 TA all sites 1 300 to 1 307.txt FAA N90 TATUTG unk site 1 300 to 1 307.txt FAA N90 TG all sites 1 300 to 1 307.txt FAA SWF ASR UAL1 75 and AAL1 1 1 230 to 1 300.zip FAA 8 ...\UAL175\UAL175 ZBW ual175 and aalll ZBW 1233 to 1315.txt FAA ual175 ZBW 1210 to 1330 1470 code only.txt FAA ual175 ZBW 1244 to 1303.txt FAA .■■\UAL175\UAL175 ZNY uai175 zny 123730 to 124130.txt FAA uall 75 zny 1 23920 to 1 24430.txt FAA uall 75 zny 1 242 to 1 246.txt FAA uall 75 zny 1245 to 1249.txt FAA uall 75 zny 1 245 to 1 249b.txt FAA uall 75 zny 1 248 to 1 254.txt FAA uall 75 zny 1251 to 1 257.txt FAA uall 75 zny 1 251 to 1 25930.txt FAA uall 75 zny 1 25620 to 1 301 50.txt FAA uall 75 zny 1 258 to 1 304.txt FAA uall 75 zny 1 300 to 1 304.txt FAA uall 75 zny 1 301 30 to 1 304.txt FAA United Airlines Flight 93 .■AUAL93 UAL93 Beacon JFK and EWR ASR.txt FAA ual93 PIT Tracon 1 300 to 1 440.txt FAA ..■\UAL93\Processed UAL93 Ual93 back exported from RVP, don't use D targets.urf 84^ RADES Ual93 combined NTAPs unfiltered. urf 84 l RADES Ual93 combined NTAPs. rad 84^ RADES ual93 end segment back exported from RVP.txt 84 RADES Ual93 end segment only. rad 84 RADES Ual93 from RS3.rad 84* RADES ual93a export from RS3.txt 84 RADES ual93b export from RS3.txt 84 RADES ual93c export from RS3.txt 84 RADES 9 ■ -.\UAL93\ZDC UAL93 ual93 all zdc ntaps merged together.txt FAA ual93 zdc 1 305 to 1 325.txt FAA Ual93 zdc 1 31 8 to 1 320.txt FAA ual93 zdc 1 324 to 1 330.txt FAA Ual93 zdc 1 324 to 1 330a.txt FAA Ual93 zdc 1 324 to 1 330b.txt FAA ual93 zdc 1 325 to 1 345.txt FAA ual93 zdc 1 346 to 1 356.txt FAA ual93 zdc 1 353 to 1 403.txt FAA ual93 zdc 1 354 to 1 359.txt FAA ual93 zdc 1 354 to 1 359a.txt FAA ua!93 zdc 1 402 to 1 41 0.txt FAA ...\UAL93\ZNY UAL93 ual93 zny 1 239 to 1 249.txt FAA ual93 zny 1 245 to 1 255.txt FAA ual93 zny 1245 to 1255a.txt FAA ual93 zny 1 25430 to 1 304.txt FAA ual93 zny 1 300 to 1 31 0.txt FAA ual93 zny 1 306 to 1 31 6.txt FAA ua!93 zny 1 31 230 to 1 32230.txt FAA ual93 zny 1 31 8 to 1 324.txt FAA ...\UAL93\ZOB UAL93 ual93 zob 1 255 to 1 300.txt FAA ual93 zob 1 330 to 1 334.txt FAA ual93 zob 1 334 to 1 338.txt FAA ual93 zob 1 338 to 1 342.txt FAA ual93 zob 1 342 to 1 346.txt FAA ual93 zob 1 346 to 1 350.txt FAA ual93 zob 1 350 to 1 354.txt FAA ual93 zob 1 358 to 1 402.txt FAA ual93 zob 1 402 to 1 406.txt FAA ual93 zob 1406 to 1410.txt FAA 10 Airport ASR Data ..AUnderlvinq ASRs BDL Approach TDTG 1200 to 1300.txt BOS Approach TD 1 200 to 1 228.txt BOS Approach TD only AAL11 UAL175 and DAL1989.txt BOS Approach TG 1 155 to 1355.txt Cape Approach TATUTG 1 200 to 1 300.txt MHT Approach TATUTG 1200 to 1300.txt PVD Approach TDTG 1200 to 1300.txt Read Me.txt UAL 175 ABE CDR TATUTG 1243 to 1256.txt FAA FAA FAA FAA FAA FAA FAA FAA Section IV - Ground Tracks Description The following figures show the ground track of all four hijacked flights, American Airlines Flight 11, United Airlines Flight 175, American Airlines Flight 77, and United Airlines Flight 175. The ground tracks are based on radar data obtained from the Federal Aviation Administration’s Air Route Traffic Control Centers and the U.S. Air Force 84th Radar Evaluation Squadron. Where available, flight data recorder (FDR) information was used to supplement the radar data. All figures show the ground track of the flights overlaid on a simplified map of the northeast United States. The first figure shows the entire ground track for all four flights. The subsequent figures show the ground track for successive 15-minute periods, as specified on the figure. In these figures the entire flight path is shown with a dotted line, and the ground track for the specified 15-minute period is shown with a solid line. The beginning of the solid line corresponds to the initial time specified, and the end of the solid line corresponds to the final time specified. The figures shown are: Figure 1 : Ground Track for duration of all flights Figure 2 : Ground Track for all flights, 8:00 AM through 8:15 AM Figure 3 : Ground Track for all flights, 8:15 AM through 8:30 AM Figure 4 : Ground Track for all flights, 8:30 AM through 8:45 AM Figure 5 : Ground Track for all flights, 8:45 AM through 9:00 AM 11 Figure 6 : Figure 7 : Figure 8 : Figure 9 : Ground Track for aii flights, 9:00 AM through 9:15 AM Ground Track for ail flights, 9:15 AM through 9:30 AM Ground Track for aii flights, 9:30 AM through 9:45 AM Ground Track for ail flights, 9:45 AM through 10:03 AM Senior Aerospace Engineer 12 Ground Track of all flights 08:00 through 10:03 AM --" 4 . co Ground Track of all flights 08:00 through 08:15 AM o LL Ground Track of all flights 08:15 through 08:30 AM Ground Track of all flights 08:30 through 08:45 AM ' i VC : - v- •. \ \\ -V \ /I V . *V L - T— T— lO r- x: 05 r-- .03 CO C3 1 * GI 03 LL 03 03 " 0 * 0 LL 0 LL _c 0 _C 0 s_ 0 s 0 < _C < C f— i — r— tZ 03 < 0 < O ~a o ~C u 0 0 -•— > *u 0 0 E 'a E E < 3 < 3 jcT 3 - »■-. • V •/ » s .._ • V t • a t , Jr- * . 5 ) < 3 p LO • a 00 o Ground Track of all flights 09:00 through 09:15 AM oc Ground Track of all flights 09:15 through 09:30 AM U ON \ Ground Track of all flights 09:30 through 9:45 AM O